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When should lower radiator hose get hot?

Finished replacing my water pump (64k miles), belts, and upper/lower radiator hoses (and,of course, the fan shroud that got trashed when the water pump went out!).

Filled radiator through expansion tank. Started car. It warms up to th 12:00 needle position on the gauge after a few minutes and drove around block. Gauge stayed at straight up position, tons of heat blowing into cabin.

Pulled back in garage. Top radiator hose HOT - but bottom hose cold.

What's going on? Do I have air in the system? Shouldn't the coolant in the radiator be circulating through top and bottom hoses all the time? Over-filled?

Why no answers? Is it a stupid question? nt

Re: When should lower radiator hose get hot?

Not a stupid question. Lower hose will get hot as water circulates through the radiator - which is not necessarily all the time. It will circulate when the thermostat opens up, after the engine reaches operating temperature, which will depend on the setting of the thermostat. Some open at 180F, others 195F, etc.

Did you replace the thermostat? It could be malfunctioning. Or perhaps the engine has just not warmed up enough for the thermostat to open. Air in the system is a slight possibility, did you follow the Bentley procedures for bleeding?
Ernie Peters
2000 steel grey 2.3 5spd
1996 318ti arctic silver 5spd (deceased)
2004 X3 2.5 black auto
1992 Volvo 240 red metallic automatic
1988 Mustang 5.0 LX red 5 spd
1970 Lotus Elan S4 (latest addition to the stable)
1956 Chevy 150 454 big block hot rod black automatic

Re: When should lower radiator hose get hot?

Thanks for reply.

Did not replace thermostat. And today I removed about a pint of coolant and drove further. Apparently, the last time it did not get hot enough to open the thermostat. This time, I turned off the heat and turned on the AC, trying to get the engine hot. Gauge stayed at noon position and lower hose got warm. Got a few bubbles out of bleed screw on expansion tank (2000 2.5). So all is okay. Just need to keep an eye on the coolant level now, I guess.